The AM Forum

I am waiting for a reply from Cushcraft for this problem, but I would like to pose a question to the board also.
I set the measurements for the middle of the band for 20M, 15M and 10M. 10M is about 3:1 SWR near the AM Window 29.100
The Driven  element becomes a rotating dipole for 40M and I set this up for 'middle of the band' also and I discover that I  have 3:1 SWR at the high end of 40M, right at the AM Window. DAMN!!!
You don't find any of this crap out until it's off the ground.
My question is....Will it hurt or destroy any of the RF components (traps) running 200 watts AM??? That would translate to 800 Watts P.E.P.

Thanks

Fred

Hi Fred,

That's a good question.  I'm not absoultely sure, but will take
a shot. At first I thought yes, a high swr would be a problem,
but after thinking about it, maybe not.

I guess the question is, if you swept that trap Yagi from 14mhz to
30 mhz continuos - with 1500W, would it do trap damage?

I would think that the maximum voltage across each trap would
occur at its tuned resonance spot, being a parallel tuned circuit.
And, at freqs other than resonance the trap would have minimum
voltage across it. So, generally a high SWR caused by being off
freq is not a problem, voltage arc-over-wise..

Also, since a mismatched feedline puts less power into the load,
you will have another buffer when off freq.

I think the problem is that even though the difference between
a 3:1 and 1:1 swr is probably not noticable on the air unless
you have a VERY long feedline, your radiation pattern could
go to hell.  ie, trap Yagis are inherently more narrow than
full-sized Yagis, and both the driven el and parasites use
similar designed traps. So, if you are seeing a 3:1 swr on
one end of the band, chances are that the reflector and
director are affecting the pattern enough to make your
front to back poor.

Do you have the published SWR curves and F-B curves
to compare against?  The f-b is easy to determine with
a turn of the beam. Make sure everything is working as
designed.

But, to answer your question, NO I don't think a 3:1 swr  
[or even higher]  will hurt anything on the beam, if my
assumptions above are correct.. Esp at only 800W pep.

Maybe some other guys here will have opinions on the
things discussed above.

Please let us know what the manufacturer says when they
get back to you. You've got me curious.

73,
Tom, K1JJ

Fred:

Do you have a MFJ 259B or grid dip meter?  If so, have you swept the antenna to see if it dips and reasonates somewhere outside the bands?  

Am not sure how the feedline is matched to the elements, gamma, balun or what.  I had a similar problem and found the stuff I used to seal the coax at the split for the feed was causing a problem.  I cut the feed end off and remade it, then used something that was not reactive at RF and mine (not a Cushcraft) came into the band.

Following up on Jim's comments...

Fred, what does the swr read in the middle of the band where
you set it? ie, are you seeing near 1:1 there, but are not happy
with the sharp curve?

Even my HB 3el 40M full sized Yagi with a 1:1 swr in the middle
of the band, I see the swr creep up to 2:1 on the band edges.  

Check the published curves against your actual readings if the
center readings are good.

T

Thanks guys,
Thankfully I did not use anything on the connection to the driven element. I did spray a non conductive coating of a Plastic spray on the insulator only. There is 1 inch of no spray from the insulator and the actual driven element parts. And I sprayed this plastic insulator ONLY on the screws where the connection is made to the driven element. So, I don't think there's some weird RF leakage path in what I have done. This was done on the recommendation of Ed Hammond, (tech help at Cushcraft) before I had the antenna mounted on the pole. He actually suggested a varnish used by Marinas in case there was something conductive across the insulator to the driven elements.
My MFJ guy is telling me that the antenna is responding to the measurements for the middle of the band very nicely. 20M and 15M are very happy. 10M should have been set for the upper part of the band, I guess. It's just the sharp rise to 3:1 SWR for 10M and 40M that I'm concern me.
I'll confess that I do not have a connector on the loose end of the RG-213. I just jam the center wire into the Type-N female on the top of the MFJ and a clip lead for the ground. Maybe this is a nasty 50 ohm connection. It's been to blasted hot out there to put a PL-259 to do these measurements properly.
But I thank you for the responses and look for more from my remarks above.

Fred

The correct connector will make some difference Fred.  I will be curious to know what you measure when you have it on.  Most of the difference may just be impedance.  Of course the 259B is designed for 50 ohms, it will measure out of that range but the readings are a bit off.

Fred,
Try sweeping the ant to see if there is a low vswr point to determine if the resonance has shifted or there is a real failure. fc

Hello all,
I received a response from Cushcraft about the 3:1 SWR on 10M and 40M and the following was all I got!

OM    the stingers at the end of the driven element must be peaked for the part of 40M    it cant be set at 7.050 for CW at the low SWR and then used at 1 KW  for AM   about 200 watts into a tuner  no problem      Ed Hammond Wn1i

Ed was helpful in the beginning about some questions on the install and the vague instructions for the 30/40M add-on, but the above response didn't help at all.

So, yous guys say that with 200 Watts AM there should be no melt down.

The only other thought that Ed didn't address in my e-mail was the alignment of the elements.

The director is not lined up with the other two elements.

Of, course this shows up when the antenna is off the ground. I was so beat from the things that went wrong with the install of the pole that I didn't notice this. The yard was a wreck from the big crane truck, and I was suffering from heat exhaustion. Believe me, I paid for it the next two days. It doesn't matter how much GATORade and water you drink. IF YOU ARE BECOMMING AN  OLD FART the high heat and humidity WILL get you.  And my wife wonders why I can't take the heat in the Philippines......haaaa haaaaa !

Thanks for reading the latest from MOP radio.
And the advice is always welcome. I think I'll have a good station back on the air in a couple of weeks. I'm still priming a dark green color in the 'shack' so, I can proceed with the install.....220VAC, grounding,,,lightning protect...........etc, etc

73     Fred

Fred,
You should have built a Log preiodic. I was not impressed with any crushcrap products when I was looking for an antenna. I made the mistake of buying a tennadyne T12 log. Very good electrical design but mechanical hunk of crap. I wouldn't let my kids play under it. I just about doubled the weight to make it strong enough. Tom Vu has built a couple logs and I bet he spent less money than I did. sorry om the lack of support means only 1 thing. Spread the word about th ecompany so nobody else gets screwed. Tell them of your plans Too.  fc

Fred,
So sad to see you going thru this BS at the hands of the
commercial antenna makers. I agree with Frank - I've
seen their work and gag  inside every time I look closely
at their element mountings, boom materials and general
structural integrity.  Just imagine that Frank had to double
the weight of his Tennadyne log to make it air worthy. I
was at his place and saw his mods and they were right
on the mark.

Anyway... there is no need for an expensive crane to put
up a Yagi. Run a 45 degree angled "tram-line" rope from
the ground up to the top of the tower. The Yagi slides up
on a pulley pulled by another rope and pulley. Use a
come-along to position/pull it up on the top mast mount.

I also agree with Frank on building a log. I would take
that trap Yagi down, [with a tram line rope] pull it apart
and use the materials to build a nice 13-30mhz log periodic.
Go to the metal scrap yard to fill in the missing aluminum
for CHEAP. Put the new traps on e-Pay for some sucker who
blew his own out.

You could get the Tennadyne 30' boom element spacing
and length details and duplicate it in your heavier duty version.
Bullet proof.

You will learn a lot in the process, which is the best part.

Here's  the 12-33 mhz JJ stacked log periodic system - homebrew
and put up with a tram line rope at 100' and 60'.  Top log is 60'
boom, 400 pounds, overkill - been up for 6 years now. Bottom
log unfinished, good for 20M for now. Notice the "star guying", 6
point guys connected to HB steel triangles to greatly reduce tower
twist from the antennas:
(http://home.comcast.net/~k1jj/wsb/media/254120/site1065.jpg)

my log is 30 feet long boom with 12 elements at 67 feet. Takes power like a dummy load. My log is about 90 LBs.
My heart sunk when I opened the box my antenna came. I felt taken.
I informed tennadyne of my feelings and share them every chance I can.
Electrical performance is very good. I've also had this conversation with the new owner.
I wanted them to make a heavy duty version that would be very cool.

Tom saw my design and built an even stronger one.

Dean KNX and I walked it through the bands one Saturday morning running about 50 watts. Chuck was on the side to strap me with his stacked logs.

I seem to remember when you told the Tennadyne guy that his
log wouldn't last long, he said to you something about hams taking
down their antennas every few years anyway, so what's the
difference?  How did that reply go?... :lol:

Well, believe it or not, I'm on my way out to work in this heat to
do some needed overhead and side trussing on the new 6M array....

T

YUP, then I told him I just took down my homebrew Quad that was up 19 years.  

The only thing you can do is spread the word to protect your friends.
The hardest thing about homebrew antennas as you know is finding a source of materials. Just think how a little find like Frank in W. Hartford
made all the difference in the world for both of our projects.

G.L. on the project. I'm almost done sheet rocking the ceilings so know about generating sweat.

I am not suprised at the response you received from Cushcrap.  I have a Mosley TA 53 and on the first assembly, I ran into problems which prompted a couple of calls to them.  The first call was reasonably congenial, but the second one was as if I was trying to get company secrets.

They act like, we sold it, you fix it.  The only company I have dealt with that was very nice across several conversations was Hustler (Neutronics)  I have one of their 5BTV antennas and spoke about moving the 20 meter section to 17.  They were very nice and made repeated suggestions (it never did work, so don't try).

The Mosley is made well mechanically, fit on the lot and gove me the frequencies/bandwidth I wanted.  I have moved it 4 times and each time it went together without problems.  I like the log periodic thing, but you have reduced front to back gain to get the bandwidth.  However when the bands are in, who cares.

A fellow named Curt Steuba (sp) writes a good column about antenna (called Aerials) in that magazine from Calif. that looks like a tabloid.  I can't remember what it is called, but he lays it on the line.  My kind of ham.

Hi Jim,

This is an interesting topic. Many opinions, of course. Here's
mine...

Generally speaking, you are correct. There's no free lunches. But
there are many variables to consider. This is the case when looking
at the smaller, compact logs and ones that are poorly designed, or
when a Yagi is tuned for max f-b. ...  But, boom for boom length, they
are within a db of gain and the f-b is similar to a Yagi when the Yagi
is tuned for reasonable forward gain. A Yagi tuned for MAX
forward gain has a f-b of maybe 15db, so a log may have a better
f-b in that case. A yagi tuned for max f-b can exceed 45db over a
narrow range, but will lose a ~ db in forward gain, thus back to par
with the log. [of similar boom length]

Logs get a bad rap sometimes. I thought the same thing before I
looked into them closely.  A lot depends upon the design
and implementation. There are a few commercial logs out
there that use openwire line to inter-connect the els. Big
mistake. The eles are ~ 70 ohms and need a good set of 3/8"
spaced 1" angle aluminum or a double boom to simulate a 70
ohm feedline. Without that some els will hog RF and others will
go along for the ride. Axe Chuck/K1KW about his ideas on this.

As for front to back, mine gets close to 25 db on 20M  and
sometimes 30db + on 15 and 10M, and the Warc bands.
There are times when I turned the log and could not even
hear guys who were previously in there with decent signals.
Especially on the bands above the lowest design freq, there's
a lot of "reflector aluminum" behind the driven el...  :D

As for forward gain, yes there is a compromise, and much
depends upon the log's taper and spacing factors. You can
put up a 13-30mhz log with a 20' boom and it wud be lucky
to perform like a 2el Yagi, poor 12db f-b, etc. BUT, put up one
that covers the same freq with a 60'++ boom and you are
seeing performance that equates to 4el Yagi monobanders.  
Chuck/K1KW, who also has a HB stack of 60' logs, says that
they are the equiv of a  4-5el Yagi monoband stack - but
covers 13-30mhz continuous!  But, as you suggested, you can fit a  
wide spaced 6el monoband Yagi on a 60' boom with somewhat
better performance than the log.

Also, consider the fact that logs are virtually unaffected by
tower problems, like guy wires, other beams,  ant wires, etc.
Being a closely spaced, all driven cell, they are not like a Yagi
whose performance can be destroyed by surrounding objects.
I wud venture to guess that many hams with Yagis that are
stacked with other beams and guy wires  "think" are working
well but are not. It takes very little to ruin a f-b on a sharply
tuned Yagi. A log can actually sit 5 ft off the ground and still
work with a pattern. The take off angle will be very high, but
the elements will still have the proper phase relationship,
though pulled down in freq.

BTW, Chuck/KW has been known on the 10-20M bands as
having probably the biggest signal and best ears in North
America. He gets on and the pile ups are bedlam.

As you can see I love the log periodic, and when we consider
that there is no el tuning required, the gain and f-b, AND SWR
stays within a reasonable limit from 13-30mhz, the gain and
f-b rival big monband Yagis [assuming they are big logs], it's
a hard combo to beat.... :D  But takes more effort, more
elements, to build a big set of logs - no free lunch.

BTW, modeling a log with just 180-0-180-0, etc feed will not show the
full gain. Using Nec and a simulated feedline is closer. According
to Chuck, there is a capacitive charging effect on the smaller elements
in front of the normal cell that adds to the gain and will not show up
in some models. I've never verified this, but thought I'd mention it.

73,
Tom, K1JJ

There you go getting real techincal on me.  Most of us have a modest budget for tower and rotator.  You are very correct on all you stated Tom but in my case and most people the size to get what you describe would involve a LOT.  

I sure wish I had the support and rotator to support a proper log.  I worked around a 25 KW log one time.   The boom was approaching 100 feet.  What an antenna, and works just as you describe.  But for a 16 ft. boom I see about 13 dbd average on everything but 12 meters for f/b and about 7 dbd forward.  For a 16 ft. boom that works for me. :roll:

The real good point of the LP is the effect of surrounding items as you describe.  As for SWR, as long as it doesn't hurt the feedline or transmitter, I don't worry about it, efficiency is what counts.

If you should come up with another tower, rotator and LP like yours, please deliver and install, I will furnish beer and pizza.  Oklahoma is a short drive for an 18 wheeler. :D

OK Guys
This has been educational indeed. I'm sorry I do not have a lattice tower. It was going to be twice the price plus dealing with municipalities and permits and all that didn't interest me. So, I'm stuck with a nice 75 foot utility pole. Any time there's a problem with the Cushcrap I'll have to hire the crane and a hardy soul who will do any necessary maintenance.
Most of the Hams here in town are too old to climb. There are 6 Hams within 5 miles of me. I'm sure they will love the AM carrier. Hopefully they are 2M types.
I'll give you some feedback when I get a connector on the coax and do some serious sweeping with the MFJ.

There was one other question I had about the elements not being perfectly aligned to each other. The Director is off a little. Hopefully no big shakes.
[/b]

Hi Fred,

No, the slight misalignment [I assume it's like 5 degrees max?]
will have no effect you would ever notice. Their average distance
spacing apart is still the same, so the tuning will be OK. If the el
alignment was off by say, 15 degrees or more, then you might
BEGIN to see coupling problems between els and the pattern wud
start to deteriorate.  

Jim...  Yes, I fully understand the tower/QTH limitations. You do
what you can do with what you have, for sure.  

There's been places where I've read that logs were simply a
bunch of dipoles that had no pattern at all.... just a broadbanded
discone type ant.  :roll:  I just wanted to express the fact for the
BB readers that may not be aware,  that logs indeed have very
strapping patterns and have their place.  In fact, if I were limited to
a single 30' boom antenna, it would indeed be a 12 el log like what
Frank has up. It would be a wee bit more work than a TA-33, but even
a  Rohn 25 tower would handle it.

Thanks for bringing up the point, OM.

T

Tom Vu,
You forgot to mention front to side on the log. I have never seen an antenna that matches the front to side. front to back. That is what QRO
dusts away.

Fred:  Perfect horizontal alignment should not be necessary, if it is that critcal, something is wrong.  Get the connector on there and get the readings.  I will be curious to know.  

One of the worst antennas I have ever used is the KT 34 by KLM.  Compared to others it had good F/B and gain, but mechanically was a nightmare.  It isolated the elements from the boom and used some sort of plastic attachment points.  Wind is West Texas would move those in no time.

I sure wish I had the room and support structure for a 30 ft. boom.  I would have a LP up in a heartbeat.  Wait a minute, you are talking real money.  You know " a billion here and a billion there and the first thing you know you are talking about real money".

I've been running a Wilson System 1, 5 element tri-bander, since 78. The only time I had to take it down was in 91 to repair some wind damage to the top of the tower. At that time I replaced all the beam nuts, bolts, U-clamps, and saddles with stainless steel hardware. Great antenna.

Jim,

You bring up a good point about element spin on
booms.  Nothing looks more JS than a Yagi that's sitting up there
with spun eles after a wind storm... :lol:

I've had a few do that in my earlier years...mostly becuz
of high winds and using only u-bolts.

But at this point, all of my elements are double u-bolted AND
pinned to the boom with bolts right thru the el plate and boom.
Even the 6M els are pinned. It's EZ to do and becomes bullet
proof in the highest winds and ice loading.

As far as $$... look up the scrap metal yards in your area. The
one I hit had YEARS of built up used aluminum boom and
element material. $1.50/pound.  It seems no one uses this
stuff for much, so the selection can be FB.

I've built some elaborate antenna arrays for under $200 of
aluminum. [That's 133 pounds of alum stock].  They have
1/4", 3/8" plate, etc for your brackets too.

Bob, K1KBW just built a 4 el 6M Yagi, complete, for $21 of
alum from this place.  

Check out the steel area for bargains on masts, etc. too

Frank, yes, the front to side on a log is good. Though, even a
dipole has a great f-s ratio, right?... :D    I'm curious  what ant
situation you are comparing the log's f-s to?

73,
T

Tom:

In Oklahoma the junk places only have old cars and refrigerators.  I probably would have to import the materials :)

Jim,

Do a search for metal recycling companies and metal dealers with
used metal.  Check the phone listings and also call the local
machine shops. The owners usually know where to find this
stuff used.

If they don't exist in Oklahoma, there's a big opportunity for you... :D  
The guys I know in this area doing it are millionaires as a result.  
BIG business this recycling. The prices on copper, alum and steel
are the highest in years with a big spread to work with.  They hold
the best scrap and put in on racks for retail business too.   Check
around..

T

tom
I was turning the antenna while W1AW was transmitting and found the null very deep FS.   I get about 15 dB on 20 M and over 20 dB on 10.

I took the tennadyne square booms and welded sleeves into them.
Them put fiberglass blocks between both booms with holes for the elements. Nothing has moved since '97. It had about 1/2 inch of ice
a couple times.

Yup you can build antennas a lot cheaper than buying them. it is a lot of fun. I was amazed how well it worked 6 feet off the ground. The best place for stainless is mcMaster but the Boston Whaler boat place in Niantic
is also quite cheap.

OK Folks here are the results from an installed connector on a 150 foot run of coax going to the Cushcrap A3S

40M 7121 1.7:1 SWR  Rs40 Xs 20
       7290  3:1 SWR    Rs 26 Xs 59    160kc BW?

20M 13.99 2:1SWR    Rs 62
       14.09 1.3:1 SWR Rs 55
       14.300 2.5:1 SWR Rs 19 Xs 11
       14.286 2.5:1 SWR Rs 21 Xs 11

15M 21.100 1.5:1 SWR Rs 41 Xs 15
       21.370 2:1 SWR    Rs 50 Xs 34
       21.450 2.5:1 SWR Rs 30 Xs 33

10M 27.928 1.7:1 SWR Rs 47 Xs 27
       28.5     1.5:1 SWR Rs 54 Xs 12
       28.9     2:1 SWR    Rs 36 Xs 26
       29.2     2.5:1 SWR Rs 20 Xs 11

I guess the next time I'm rich, I'll have the elements shortened to get me  more on the 'phone side /AM of the all the bands. Right now I'm going to run it like it is, unless someone sees the above numbers as waaay out in the left field.
Thanks for looking and I like the new location .
FRED MOP Radio   

I guess the readings look reasonable, Fred.

Though, the only way to tell what's really happening at the antenna feedpoint is to measure it AT the antena feedpoint OR use a 1/2 wave multiple length of feedline for a particular band/freq.

For example, there is probably a point where you have a 1:1 swr at the ant feedpoint on a particular freq. No matter what length coax you run, you will always see close to the same R and X  at the feedline's end connector on the ant analyzer. [when truly 1:1]

You might  sweep it and look for the 1:1 point. Then add a 1/4 wave coax length jumper [* 0.66 vel factor]  and see if R and X change  a lot. 

So, can you find spots that have 1:1 readings? I just see arbitray freqs listed with 1.5:1, etc,  And how do your curves compare to the published specs?

Yagi swr curves can get complex, not simple like a single dipole. The is cuz as you go up in freq, the director gets closer to the operating freq and lowers the input impedance greatly... and same for going down in freq as the ref gets close. A single dipole's curve is smoother and broader w/o the parasites. But this is where your gain comes from...  generally the closer the els are tuned to the operating freq, the better gain and f-b. But the tradeoff is narrower swr and pattern operating range. All a compromise. 

BTW, with that wooden utility pole... why not add spikes to climb, or bolt on a climbing ladder? You cud do all the work w/o a crane in the future.



T

Thanks Tom VU
I'll have a chance to test with different lengths of coax next week IF IT COOLS OFF.  The best way to check this operation out is to use it and see how the FB ratio is doing for the various bands. I realize that 40M is just a dipole up there.
The utility pole would be very hard for some one to work. A lattice tower enables the climber to strap on to something and work. This pole is pretty fat and the climber would have difficulty reaching around to strap himeslf in.

Has anybody heard of the STEPPir antenna. It sounds pretty neat with the elements continually adjustable from down in the shack. I guess what's up on the tower are hollow fiberglass rods and motors extending and retracting the actual metal elements inside. THey say you can even switch directions without turning the aerial

Fred

Hi Fred,

Well, remember that it's easy to get a good f-b on most any LOSSY directional antenna. Even a loopstick with a tiny whip sense antenna showing -25dbd gain on 75M can show 30 db f-b...  A Yagi that has normal trap losses, water in the connectors and feedline, poor/rusted hardware, etc and 6:1 mismatch swr resulting in a NEGATIVE 10 db forward gain can STILL have a  30 db f-b and clean pattern too. A front to back test is more of a general confirmation that the reflector and director spacing and tuning are in the ballback. That's about all it will tell you.  If you take careful S meter readings using a beacon as you turn it, it will also tell you about pattern side lobes, etc, so you can verify these data against the computer model that it works as it was designed - and there's no other obstructions messing with the pattern. But generally, you will see the sharpest pattern if you can maintain a high Q, meaning connections and parasitic elements are at their lowest losses possible.

Here's my point:

What's hard to do, and is the real test, is achieving FORWARD gain. Everything has to be right to obtain it. Feedline loss, phasing, element lengths/tuning, element IR losses, obstruction attenuation, etc. The only real way to test/verify forward gain is to put up a reference dipole at the same height  in the clear away from the Yagi. If you can see ~5-6 db over the dipole with fast A/B switching most of the time, then you know the Yagi works.  Otherwise, to try to see a 5 db improvement alone by getting S meter reports or by "feel" is futile. An A/B reference is the only way.

As for the StepperIR, I've heard both good and bad. Expensive and remember that the element spacing is fixed, so it is compromised over the full 6-20M spectrum. Lots of moving parts and things to go wrong. I wud go with a log over that any day, OM. Cheaper, reliable and bulletproof. Also each "cell" is optimized for it's own freq.

BTW, bolt a climbing ladder to the face of the pole and add three small ones in a circle at the top and you will simulate a lattice tower.

73,
T

Hello Tom and  Friends of Radio
I'm gonna try to throw a small switch here at MOP radio and clutter up the  Dining Room with my TS440 and 25 watts  7290AM and give 40M a try on Monday or Wednesday afternoon between 1-3PM . I think I think I remember hearing humans talking during those times.
I'm just curious about the world of radio.  I don't know how I will act when I touch the knobs of something electronic.
I will proceed with other tests Tom has suggested here. I have to install lightning protection at the base of the pole, so there's an opportunity to see what a 65 foot length of coax reads on the MFJ compared to a 150 foot length. If it were proper at the feedpoint then the coax is just a transmission line. With ever changing SWR caused by different lengths,  then the coax is a transformer. (proper thinking here?)
Later........dudes
Fred

Fred,
How about a T tuner so you can get the swr down at the rig.  Even a series of low Q pi networks could be built for each band. Might be able to add a stub on each band to pull it to 50 ohms.

My log is well below 2:1 except for about 50 KHz around 22 MHz.
it is on R25 guyed every 17 feet. The rotor is half way up the tower with dual bearings. I used a 2 3/8 drive shaft up the middle.  Actually 13 or 14 elements would be sweet.

I was on the tennadyne site this week and now the T12 is 77 LBs up from 56. I had a bunch of emails with the new owner telling him some real feed back from us guys up here in the N.E. (price is over a grand now)
Still has some J.S.es though.

The log was a fun project and the best antenna I've ever used at 6 feed above ground. I had a quad that worked very well but wanted to add warc and was worried about interaction

Probably not Fred.  Even though I don't like Cushcrap, they do a pretty good job with the trap construction.  You might watch for warm spots on the feedline or heating in your transmitter. 

If you have a tuner that will handle the 800 watts PEP, put it in line.  It should absorb the heat for you, that is if it is at the proper point.

Thanks guys
for all of the inpoot. I'm taking this all in and one fine day there will be a signal once again from MOP radio. The move and retiring and discovering there's a baby on the way have put me through some changes that I have to deal with. I'm not good at changes.  A lot of major changes have happened  to yours truly. Things like retiring and moving and the rest of the lovely new things in my life in a matter of 8 mos. Where a normal guy will do all these things over a coupla years. I'm an O-F who decided to start a life at 58 yrs of age.Plus this DAM heat wave stops all outdoor activities. I fill sorry for you folks near  Washignton DC, MAN it's HOT.
Sorry for my sob story and the bandwidth, but I just appreciate you folks and your guidance as I get back into the swing of things.
PM's are always welcome.
MOPMAN Fred

Fred:  Some people call them challenges, others call them opportunities.  Just make the best of everything and you will have a good life  I have a 40 meter kit on my Mosley and when it was installed, I could rotate it against a signal and see when the ends passed the direction of the station.

One thing I forgot to ask.  Is this antenna new or used?  If it is used, did you check the mechanical integrity of the traps?  It is possible, god forbid, that one of them may have a high resistance connection.  My mosley is almost 10 years old and now that I am in my final destination it suddenly has an intermittent connection it seems. 

I thought it was in one of the feeline connections, but the more I look the more I think it is a trap.  The thing has a diriven element for 10/15/20 and one for 12/17.  The 10/15/20 emement seems to vary on the MFJ.  Sometimes it works as it should and sometimes the 20 meter resonance point is 13.850 or so.  When it acts up the 15 and 10 meter bands are out as well with high SWR. 

I have seen the StepIR and it looks like a good antenna, but have never operated with one.  In a corrosive atmosphere it might be a problem in a few years if corrosion builds up.

Good luck.

73  Jim
W5JO

Jim,
I've been doing a lot of reading lately on logs, stacks, etc and of course have come across the StepIR stuff. Seems the guys think highly of them. They are getting quite popular on the air too.   I haven't heard of any serious problems yet. Your concern of corrosion is important, of course. Does the mechanism breath or is it sealed?

BTW, I've decided to take down both of my logs and rebuild them into separate long boom Yagis for 20M and 10M. The bottom one is down already and disassembled. Today I may take the top one down. I removed the bottom one by myself and think I can manage the top one too...

Out of the guts I'm gonna make a  pair of 70'-80' boom 20M Yagis to stack at 60'/120' and something else like that for 10M, I think. Decided that indeed, the logs are a compromise for stacking spacing and raw gain. I never get on 15M or  17M anyway, so it was a waste. I'd rather focus on two bands and have them optimized fully.

That StepIR would be a great antenna to stack a pair.  Not sure if anyone has yet, but would be something.

T

Gee Tom,
Ever consider selling a log. That was a strapping ant.

Yeah, Frank,  I did. I was gonna axe $2K for the top one and $1K for the bottom. Considering what Tennadyne charges for their stuff, that's a steal.

But after adding up all the stainless hardware and aluminum I would need to buy again, it was a wash. Stainless has jumped in price big since I bought it before. I'll use everything on the logs and even need some additonal scrap alum to make the new Yagis. The two big 20M Yagis will be mounted on swing gates on the side of the 190'er and manually tied off. Same with the big 10M Yagis. I hate rotators. Fixed/ moveable switching directions are my thang.

I've never had up a set of big long boom Yagis on 20M before... as well as 10M, so wanted to give it a try. The difference over the logs will be marginal, but, a few db is a few db.  Plus, those big logs were starting to scare me as far as working on them. Taking one down is a nightmare with all the guys and those many els. The new Yagis will pull up the side of the self supporter with no guy wires involved. Cake to bring up and down with one person working.

T

The example I saw at a hamfest used finger stock to make the contact.  It was made by them rather than the ordinary stuff the can be bought off the shelf and was very heavy, so it might wipe any corrosion from the tube.  It would definately work FB for a long time, but as I stated, what about the long haul.  I just don't know.  But from what I observed, it should breath to a great extent.  There were no caps like the satellite guys use over the RG 6 to prevent water from running down the element toward the mast.

Your decision to seperate the antennas is sound provided you seperate them more than 1/2 wavelength which will minimize interaction.  Do you have the room to do that?  Actually more than 1 wavelength would be best, but we do as we have space and money.  With one optomized for 20 and a few KW you will blow the big guys out of the tub.  Good plan.  Same for 10, which is my favorite band, I wish I had the space to do what you are planning.

OK, Jim -

Does the StepIR work with metal tape [like a tape measure] inside a fiberglass tube? So does it actually make contact with a tube? I'm not sure.  I saw one once myself at a ham fest a few years ago. If I had the technology down, maybe I'd build one up. You might try a post on  the "Tower" BB  and axe if anyone has had ANY problems with the StepIR. Esp near the ocean. They will let ya know.

As for the new Yagis...  I plan to build TWO for 20M and stack them at 60' and 120' on a separate tower that just has a 75M quad at the top at 190'. So, they will be alone, more or less. The 10M ones are still being planned, but will probably be a pair on another tower, but similar in scale, etc. No interaction problems, the towers being about 150' apart.  We'll see how it goes after the alum is on the ground and how the antenna design greed goes later... :-)   The bull work is today, taking down the 400 pound log from 100'... oughta be sporting.

T

Tom:

I turly have forgotten how they were constructed.  But it seems as if copper tape is attached to fiberglass poles that collapse is the contruction. 

I found their website and here is how they describe the antenna, which is different from the one I saw.



 Each antenna element consists of two spools of copper strip conductor mounted in the antenna housing. The copper strips are perforated to allow a stepper motor to drive them simultaneously with a sprocket.

Stepper motors are well known for their ability to index very accurately, thus giving very precise control of the antenna length.
In addition, the motors are brushless and provide extremely long service life.

The copper strip is driven out into hollow, lightweight fiberglass support elements, forming an element of any desired length up to 36’ long. The fiberglass poles are telescoping, lightweight and very durable. When fully collapsed, each element measures 53” in length.

The ability to completely retract the copper antenna elements, coupled with the collapsible fiberglass poles makes the entire system extremely portable. The antenna is easy to assemble, and can be installed on the ground or up on the antenna tower using our Boomslide™ assembly system.





I still wonder about the copper oxidizing over time at connections points.  My Mosley beam uses copper/bronze lockwashers between the driven elements and the phasing tubes.  I have had the beam up in dry as well as high humid locations and when I put it up here, I didn't check those little lock washers.  The antenna, because the lockwashers have oxidized, now is out of tune.  I also wonder how long term the operation of the little motors will be.

I am trying to locate some stainless steel washers to replace them.  In the area I live in, they bearly know what Zinc/Steel is.  I keep joking about this part of OK, but it is true.

Jim

Hmmm... from the description I can't figure out if the fiberglass tubes actually move for freq changes or arte fixed. Maybe they are talking about disassembly for shipping, etc.

I would rather they used FIXED hollow tubes and let the metal tape move inside. No reason to have moving mechanical tubes to fail.  The solidary moving tape sounds like an easier solution to me.

One thing I've wondered about is how vunerable are the motors to lightning?  I've lost a number of relay coils out on the tower even when lightning struck far away. Maybe they have it covered using MOVs or something.

Let me know if ya hear anything concerning  crap outs.. Seems to be a great product so far, though. 

T